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Irene opens a channel for man-made damage to rivers

The very severe damage in Vermont caused by Tropical Storm Irene led to an impressive and encouraging recovery effort both by state government and residents, many of whom volunteered to help their neighbors salvage and rebuild.

Unfortunately, however, the storm – the second flood of historic proportions in the state this year – also seems to have washed away much of what we have learned about the dangers of digging gravel from streams and rivers.

In recent weeks there have been dozens of excavators and bulldozers in rivers across the state digging gravel, channelizing streams and armoring banks with stone, not only at great ecological cost, but – particularly in the many cases in which a true emergency did not exist – greatly increasing the risk of future flood damage.

Meanwhile, the state, by not setting and enforcing clear limits on that work in the rivers, has done little – at least so far – to prevent the damage.

Knowledge gained by the scientific study of these river systems, also known as fluvial geomorphology, leaves little doubt that increasing the speed of water by turning streams that meander over rocky beds into straight chutes with little structure not only destroys vital habitat for fish and other creatures, it also increases the potential destructive power of floods. It was advances in this physics-based science which led to significant limitations on gravel removal from Vermont rivers during the last two decades.

Rock River

However, the recent flooding (and statements by Vermont Gov. Peter Shumlin) has given new life to an outdated and inaccurate idea that removing gravel from the rivers is what prevented flooding in the past. This notion ignores the fact that restricting rivers into a man-made channel, cutting off the access to flood plains and jarring mature streams back into instability the risk of flood damage is significantly increased, particularly for neighbors downstream.

More on this subject can be found in a Burlington Free Press column here and in a Vermont Public Radio news story here.